Research On Generalized Design Oriented Product CAD Model Retrieval Method

The design process of complex product evolves from abstract to specific.Designers usually start with sketches,and gradually refine each sub-modular by understanding product requirements and design factors.Substantially,it is a top-down generalized product design process that can be divided into conceptual design,preliminary design and detailed design process,and the information structure and design missions of different design stages are different.Based on this,this paper proposes a technology system and application framework,and carries out research on 3D CAD model retrieval technology for product generalized design.The structure of the thesis is arranged as follows:Concept design of product 3D CAD model push method based on sketches.This method carries out similarity measure in the product model image database by extracting the shape characteristics of product model sketch in conceptual design stage based on two stage similarity evaluation method of spherical harmonic descriptor and 2D shape distribution algorithm,which can push model consistent with the intention of the product conceptual design to speed up transformation from conceptual design into detailed design.3D CAD Model Retrieval Algorithm Based on Distance and Angle Distributions.Firstly,a large number of random points on the model surface are taken,and the length of the directed line which constructed between two random points is computed,also the angle between the normal of the point and the directed line is computed.Then,a distance-angle planar grid is constructed to express the distance-angle distribution by obtaining a statistic data of the sampled points.At last,the Manhattan distance metric method is used to compute the similarity between the two distance-angle matrices,which can give the similarity coefficient for two compared 3D CAD models.This method can effectively solve the connection between product conceptual design and detailed design.A Method of Typical Structure Mining in 3D CAD Model and Similarity Estimation Based on Simulated Annealing Algorithm.At first,attribute adjacent graph of CAD model is established through extracting topological and geometrical information from the 3D CAD model represented by B-rep,which can record face and edge detailed structure of 3D CAD model and its organization and association.Then,according to its description carrier,association graph and association graph matrix is established with the mapping relation of vertex and edge in attribute adjacency graph between typical structure and CAD model,and a mechanism of similarity estimation is proposed at the same time.At last,typical structure mining in 3D CAD model is accomplished based on simulated annealing algorithm through excavating maximal clique in association graph,while similarity estimation between typical structure and return model is accomplished.This method can realize product model detailed design.In order to examine the proposed methods,we design a generalized design oriented 3D CAD product model similarity evaluation 3D CAD model retrieval prototype system.Its functional structure,architecture,and the experimental results are presented in this thesis.